LANSING — Democrats Barack Obama and Joe Biden will be in Detroit Sunday to talk to voters about something that's turning into Obama's strong suit: the economy.

But it's also a strategic visit, aimed at encouraging as many Obama supporters as possible to register to vote by the Oct. 6 deadline.

The Democratic presidential candidate has been a huge favorite with young adults, some of whom have never voted, and with blacks. But unless people in both groups are registered to vote, they can't help him on Election Day, something Obama plans to emphasize Sunday.

"This is a key part of our strategy and has been a key part of the Obama strategy going all the way back to the primaries and caucuses," Obama campaign spokesman Brent Colburn said Friday. "It's a vital part of our efforts here in the state."

Obama plans to ask everyone attending Sunday's rally in front of the Detroit Public Library to register at least one new voter, Colburn said. The Illinois senator, joined by Biden and the two candidates' wives, also will speak about the problems in the nation's financial sector and his plan for helping turn around Michigan's struggling economy.

But with just a week to go until the filing deadline, Obama also wants to make sure he gets every possible supporter registered to vote. Michigan doesn't register voters by party, but in states that do, efforts to sign up Democrats have far outstripped efforts to add Republicans to the rolls.

Since the last federal election in 2006, more than 2 million Democrats have been added to voter rolls in the 28 states that register voters according to party affiliation. The Republicans have lost nearly 344,000 voters in the same states.

Michigan already has a high percentage of residents registered to vote, thanks in part to efforts by the secretary of state's office to register residents when they apply for a driver's license. Of the state's roughly 7.6 million eligible voters, more than 7.2 million are registered -- around 95 percent.

More than 100,000 of those voters have been added since January. Secretary of state officials won't have a final tally until after the Oct. 6 deadline, but Obama strategists hope to raise the total number of new registrants to 150,000.

Among the places they're trolling for voters are high schools and college campuses. Friday night, for instance, the campaign was sending out its "BarackStars" -- student volunteers -- to register voters during the Heritage High School football game against Mount Pleasant High School in Saginaw.

TV actor Adam Brody of "The O.C." and Rachael Leigh Cook of "She's All That" will join student volunteers Saturday to register voters attending football games at Saginaw Valley State University and Central Michigan University.

AP Photo/Al GoldisActor Kal Penn, left, speaks to a group of students at Michigan State University, Wednesday at a campus residence hall in East Lansing. Penn and actress Jurnee Smollett toured university campuses on a voter registration drive.

And during one whirlwind day earlier this month, actors Kal Penn of "The Namesake," and Jurnee Smollett of "The Great Debaters" hit six university campuses to fire up student volunteers to go out and register voters.

With hundreds of thousands of college students nationwide, "college students can ... swing the election," Penn said after talking to about 40 students at Michigan State University.

Only 65 percent of Michigan's 7.5 million eligible voters cast ballots in the 2004 presidential election, and young voters are notorious for not getting to the polls.

But Michigan State University student Annie Wildfong, a 19-year-old from Ferndale, said many of her peers have been inspired by Obama to play a role in deciding this year's election.

"It puts us in a position of power," she said, clipboard in hand, as she prepared to register students. "I think the majority of young people will vote for Obama because they want change."

Colburn said college campuses are a good place to find people who haven't registered yet or who have moved into Michigan to attend college but not updated their registration. But the Obama campaign isn't just limiting its efforts to students. All 47 Campaign for Change offices across the state are concentrating on registering voters and identifying Obama supporters.

Taylor Nichols, an 18-year-old Western Michigan University freshman from Grand Ledge who supports Obama, has worked with the Campaign for Change office in Kalamazoo to register 60 new voters on campus so far this month.

She said some students already are registered to vote but are moving their registration to Kalamazoo so they can cast their ballots on campus rather than in their hometowns.

"For most of us, it's less than a two-minute walk" to the campus polling site, Nichols said. "A lot of people seem relieved that they're making it that easy to vote."

Michigan Republican Party spokesman Bill Nowling said his party is less focused on adding new voters to the rolls than in identifying supporters for GOP presidential candidate John McCain and then making sure they vote.

"When 90 or 95 percent of the voters are registered, it's really an exercise in diminishing returns" to target unregistered voters, Nowling said. "The real crux of the issue is how many of the registered voters are going to vote for your candidate, and how do you get them to the polls?"